The EMT modulator SNAI1 contributes to AML pathogenesis via its interaction with LSD1.

Modulators of epithelial-to-mesenchymal transition (EMT) have recently emerged as novel players in the field of leukemia biology. The mechanisms by which EMT modulators contribute to leukemia pathogenesis, however, remain to be elucidated. Here we show that overexpression of SNAI1, a key modulator of EMT, is a pathologically relevant event in human acute myeloid leukemia (AML) that contributes to impaired differentiation, enhanced self-renewal, and proliferation of immature myeloid cells. We demonstrate that ectopic expression of Snai1 in hematopoietic cells predisposes mice to AML development. This effect is mediated by interaction with the histone demethylase KDM1A/LSD1. Our data shed new light on the role of SNAI1 in leukemia development and identify a novel mechanism of LSD1 corruption in cancer. This is particularly pertinent given the current interest surrounding the use of LSD1 inhibitors in the treatment of multiple different malignancies, including AML.

Microbiome-induced antigen-presenting cell recruitment coordinates skin and lung allergic inflammation.

BACKGROUND: Allergic skin inflammation often presents in early childhood; however, little is known about the events leading to its initiation and whether it is transient or long-term in nature. OBJECTIVE: We sought to determine the immunologic rules that govern skin inflammation in early life. METHODS: Neonatal and adult mice were epicutaneously sensitized with allergen followed by airway allergen challenge. Epicutaneous application of labeled allergen allowed for determination of antigen uptake and processing by antigen-presenting cells. RNAseq and microbiome analysis was performed on skin from neonatal and adult specific pathogen-free and germ-free mice. RESULTS: A mixed TH2/TH17 inflammatory response in the skin and the lungs of adult mice was observed following sensitization and challenge. Comparatively, neonatal mice did not develop overt skin inflammation, but exhibited systemic release of IL-17a and a TH2-dominated lung response. Mechanical skin barrier disruption was not sufficient to drive allergic skin inflammation, although it did promote systemic immune priming. Skin of neonatal mice and adult germ-free mice was seeded with low numbers of antigen-presenting cells and impaired chemokine and alarmin production. Enhanced chemokine and alarmin production, and seeding of the skin with antigen-presenting cells capable of instructing recruited cells to elicit their effector function, was, at least in part, dependent on formation of the microbiome, and consequently contributed to the development of overt skin disease. CONCLUSIONS: These data shed light on the principles that underlie allergic inflammation in different tissues and highlight a window of opportunity that might exist for early-life prevention of allergic diseases.

Mycoplasma genitalium and Other Reproductive Tract Infections in Pregnant Women, Papua New Guinea, 2015-2017.

Much about the range of pathogens, frequency of coinfection, and clinical effects of reproductive tract infections (RTIs) among pregnant women remains unknown. We report on RTIs (Mycoplasma genitalium, Chlamydia trachomatis, Neisseria gonorrhoeae, Trichomonas vaginalis, Treponema pallidum subspecies pallidum, bacterial vaginosis, and vulvovaginal candidiasis) and other reproductive health indicators in 699 pregnant women in Papua New Guinea during 2015-2017. We found M. genitalium, an emerging pathogen in Papua New Guinea, in 12.5% of participants. These infections showed no evidence of macrolide resistance. In total, 74.1% of pregnant women had >1 RTI; most of these infections were treatable. We detected sexually transmitted infections (excluding syphilis) in 37.7% of women. Our findings showed that syndromic management of infections is greatly inadequate. In total, 98.4% of women had never used barrier contraception. These findings will inform efforts to improve reproductive healthcare in Papua New Guinea.

A novel role for Lyl1 in primitive erythropoiesis.

Stem cell leukemia (Scl or Tal1) and lymphoblastic leukemia 1 (Lyl1) encode highly related members of the basic helix-loop-helix family of transcription factors that are co-expressed in the erythroid lineage. Previous studies have suggested that Scl is essential for primitive erythropoiesis. However, analysis of single-cell RNA-seq data of early embryos showed that primitive erythroid cells express both Scl and Lyl1 Therefore, to determine whether Lyl1 can function in primitive erythropoiesis, we crossed conditional Scl knockout mice with mice expressing a Cre recombinase under the control of the Epo receptor, active in erythroid progenitors. Embryos with 20% expression of Scl from E9.5 survived to adulthood. However, mice with reduced expression of Scl and absence of Lyl1 (double knockout; DKO) died at E10.5 because of progressive loss of erythropoiesis. Gene expression profiling of DKO yolk sacs revealed loss of Gata1 and many of the known target genes of the SCL-GATA1 complex. ChIP-seq analyses in a human erythroleukemia cell line showed that LYL1 exclusively bound a small subset of SCL targets including GATA1. Together, these data show for the first time that Lyl1 can maintain primitive erythropoiesis.

HER2-directed antibodies, affibodies and nanobodies as drug-delivery vehicles in breast cancer with a specific focus on radioimmunotherapy and radioimmunoimaging.

PURPOSE: The aim of the present paper is to review the role of HER2 antibodies, affibodies and nanobodies as vehicles for imaging and therapy approaches in breast cancer, including a detailed look at recent clinical data from antibody drug conjugates and nanobodies as well as affibodies that are currently under development. RESULTS: Clinical and preclinical studies have shown that the use of monoclonal antibodies in molecular imaging is impaired by slow blood clearance, associated with slow and low tumor uptake and with limited tumor penetration potential. Antibody fragments, such as nanobodies, on the other hand, can be radiolabelled with short-lived radioisotopes and provide high-contrast images within a few hours after injection, allowing early diagnosis and reduced radiation exposure of patients. Even in therapy, the small radioactively labeled nanobodies prove to be superior to radioactively labeled monoclonal antibodies due to their higher specificity and their ability to penetrate the tumor. CONCLUSION: While monoclonal antibodies are well established drug delivery vehicles, the current literature on molecular imaging supports the notion that antibody fragments, such as affibodies or nanobodies, might be superior in this approach.

MethPat: a tool for the analysis and visualisation of complex methylation patterns obtained by massively parallel sequencing.

BACKGROUND: DNA methylation at a gene promoter region has the potential to regulate gene transcription. Patterns of methylation over multiple CpG sites in a region are often complex and cell type specific, with the region showing multiple allelic patterns in a sample. This complexity is commonly obscured when DNA methylation data is summarised as an average percentage value for each CpG site (or aggregated across CpG sites). True representation of methylation patterns can only be fully characterised by clonal analysis. Deep sequencing provides the ability to investigate clonal DNA methylation patterns in unprecedented detail and scale, enabling the proper characterisation of the heterogeneity of methylation patterns. However, the sheer amount and complexity of sequencing data requires new synoptic approaches to visualise the distribution of allelic patterns. RESULTS: We have developed a new analysis and visualisation software tool "Methpat", that extracts and displays clonal DNA methylation patterns from massively parallel sequencing data aligned using Bismark. Methpat was used to analyse multiplex bisulfite amplicon sequencing on a range of CpG island targets across a panel of human cell lines and primary tissues. Methpat was able to represent the clonal diversity of epialleles analysed at specific gene promoter regions. We also used Methpat to describe epiallelic DNA methylation within the mitochondrial genome. CONCLUSIONS: Methpat can summarise and visualise epiallelic DNA methylation results from targeted amplicon, massively parallel sequencing of bisulfite converted DNA in a compact and interpretable format. Unlike currently available tools, Methpat can visualise the diversity of epiallelic DNA methylation patterns in a sample.

Normal DNA methylation dynamics in DICER1-deficient mouse embryonic stem cells.

Reduced DNA methylation has been reported in DICER1-deficient mouse ES cells. Reductions seen at pericentric satellite repeats have suggested that siRNAs are required for the proper assembly of heterochromatin. More recent studies have postulated that the reduced methylation is an indirect effect: the loss of Mir290 cluster miRNAs leads to upregulation of the transcriptional repressor RBL2 that targets the downregulation of DNA methyltransferase (Dnmt) genes. However, the observations have been inconsistent. We surmised that the inconsistency could be related to cell line "age," given that DNA methylation is lost progressively with passage in DNMT-deficient ES cells. We therefore subjected Dicer1(-/-) ES cells to two experimental regimes to rigorously test the level of functional DNMT activity. First, we cultured them for a prolonged period. If DNMT activity was reduced, further losses of methylation would occur. Second, we measured their DNMT activity in a rebound DNA methylation assay: DNA methylation was stripped from Cre/loxP conditionally mutant Dicer1 ES cells using a shRNA targeting Dnmt1 mRNA. Cre expression then converted these cells to Dicer1(-/-), allowing for DNMT1 recovery and forcing the cells to remethylate in the absence of RNAi. In both cases, we found functional DNMT activity to be normal. Finally, we also show that the level of RBL2 protein is not at excess levels in Dicer1(-/-) ES cells as has been assumed. These studies reveal that reduced functional DNMT activity is not a salient feature of DICER1-deficient ES cells. We suggest that the reduced DNA methylation sometimes observed in these cells could be due to stochastic alterations in DNA methylation patterns that could offer growth or survival advantages in culture, or to the dysregulation of pathways acting in opposition to the DNMT pathway.

Granulin-epithelin precursor interacts with heparan sulfate on liver cancer cells.

Granulin-epithelin precursor (GEP) is a pluripotent secretory growth factor which promotes cancer progression in a number of human cancers. However, how cancer cells interact with GEP remains unknown. In this study, we aimed to identify the cell surface-binding partner of GEP on liver cancer cells. Human recombinant GEP (rGEP) was expressed and purified to homogeneity. The rGEP was shown to trigger phosphorylation of AKT and ERK1/2 in liver cancer cells. We demonstrated cell surface attachment of rGEP, which was blocked by prebinding of platelet-derived growth factor-AA, platelet-derived growth factor-BB and fibroblast growth factor-2. Therefore, heparan sulfate (HS) had been reasoned as the binding partner of rGEP. Heparinase digestion validated the role of HS on supporting the attachment. The heparin-binding domain of GEP was mapped to RRH(555-557) in the C-terminal region. Suppression of the HS polymerase exostosin-1 reduced the rGEP binding and rGEP-mediated signaling transduction. Suppression of a specific HS proteoglycan, glypican-3, also showed a partial reduction of rGEP binding and an inhibition on rGEP-mediated activation of AKT. Furthermore, glypican-3 was shown to correlate with the expressions of GEP in clinical samples (Spearman's ρ = 0.363, P = 0.001). This study identified HS, partly through glypican-3, as a novel binding partner of GEP on the surface of liver cancer cells.

Reducing the risk of false discovery enabling identification of biologically significant genome-wide methylation status using the HumanMethylation450 array.

BACKGROUND: The Illumina HumanMethylation450 BeadChip (HM450K) measures the DNA methylation of 485,512 CpGs in the human genome. The technology relies on hybridization of genomic fragments to probes on the chip. However, certain genomic factors may compromise the ability to measure methylation using the array such as single nucleotide polymorphisms (SNPs), small insertions and deletions (INDELs), repetitive DNA, and regions with reduced genomic complexity. Currently, there is no clear method or pipeline for determining which of the probes on the HM450K bead array should be retained for subsequent analysis in light of these issues. RESULTS: We comprehensively assessed the effects of SNPs, INDELs, repeats and bisulfite induced reduced genomic complexity by comparing HM450K bead array results with whole genome bisulfite sequencing. We determined which CpG probes provided accurate or noisy signals. From this, we derived a set of high-quality probes that provide unadulterated measurements of DNA methylation. CONCLUSIONS: Our method significantly reduces the risk of false discoveries when using the HM450K bead array, while maximising the power of the array to detect methylation status genome-wide. Additionally, we demonstrate the utility of our method through extraction of biologically relevant epigenetic changes in prostate cancer.

Stability of gene expression and epigenetic profiles highlights the utility of patient-derived paediatric acute lymphoblastic leukaemia xenografts for investigating molecular mechanisms of drug resistance.

BACKGROUND: Patient-derived tumour xenografts are an attractive model for preclinical testing of anti-cancer drugs. Insights into tumour biology and biomarkers predictive of responses to chemotherapeutic drugs can also be gained from investigating xenograft models. As a first step towards examining the equivalence of epigenetic profiles between xenografts and primary tumours in paediatric leukaemia, we performed genome-scale DNA methylation and gene expression profiling on a panel of 10 paediatric B-cell precursor acute lymphoblastic leukaemia (BCP-ALL) tumours that were stratified by prednisolone response. RESULTS: We found high correlations in DNA methylation and gene expression profiles between matching primary and xenograft tumour samples with Pearson's correlation coefficients ranging between 0.85 and 0.98. In order to demonstrate the potential utility of epigenetic analyses in BCP-ALL xenografts, we identified DNA methylation biomarkers that correlated with prednisolone responsiveness of the original tumour samples. Differential methylation of CAPS2, ARHGAP21, ARX and HOXB6 were confirmed by locus specific analysis. We identified 20 genes showing an inverse relationship between DNA methylation and gene expression in association with prednisolone response. Pathway analysis of these genes implicated apoptosis, cell signalling and cell structure networks in prednisolone responsiveness. CONCLUSIONS: The findings of this study confirm the stability of epigenetic and gene expression profiles of paediatric BCP-ALL propagated in mouse xenograft models. Further, our preliminary investigation of prednisolone sensitivity highlights the utility of mouse xenograft models for preclinical development of novel drug regimens with parallel investigation of underlying gene expression and epigenetic responses associated with novel drug responses.

Hypermethylation and down-regulation of DLEU2 in paediatric acute myeloid leukaemia independent of embedded tumour suppressor miR-15a/16-1.

BACKGROUND: Acute Myeloid Leukaemia (AML) is a highly heterogeneous disease. Studies in adult AML have identified epigenetic changes, specifically DNA methylation, associated with leukaemia subtype, age of onset and patient survival which highlights this heterogeneity. However, only limited DNA methylation studies have elucidated any associations in paediatric AML. METHODS: We interrogated DNA methylation on a cohort of paediatric AML FAB subtype M5 patients using the Illumina HumanMethylation450 (HM450) BeadChip, identifying a number of target genes with p <0.01 and Δß >0.4 between leukaemic and matched remission (n = 20 primary leukaemic, n = 13 matched remission). Amongst those genes identified, we interrogate DLEU2 methylation using locus-specific SEQUENOM MassARRAY® EpiTYPER® and an increased validation cohort (n = 28 primary leukaemic, n = 14 matched remission, n = 17 additional non-leukaemic and cell lines). Following methylation analysis, expression studies were undertaken utilising the same patient samples for singleplex TaqMan gene and miRNA assays and relative expression comparisons. RESULTS: We identified differential DNA methylation at the DLEU2 locus, encompassing the tumour suppressor microRNA miR-15a/16-1 cluster. A number of HM450 probes spanning the DLEU2/Alt1 Transcriptional Start Site showed increased levels of methylation in leukaemia (average over all probes >60%) compared to disease-free haematopoietic cells and patient remission samples (<24%) (p < 0.001). Interestingly, DLEU2 mRNA down-regulation in leukaemic patients (p < 0.05) was independent of the embedded mature miR-15a/16-1 expression. To assess prognostic significance of DLEU2 DNA methylation, we stratified paediatric AML patients by their methylation status. A subset of patients recorded methylation values for DLEU2 akin to non-leukaemic specimens, specifically patients with sole trisomy 8 and/or chromosome 11 abnormalities. These patients also showed similar miR-15a/16-1 expression to non-leukaemic samples, and potential improved disease prognosis. CONCLUSIONS: The DLEU2 locus and embedded miRNA cluster miR-15a/16-1 is commonly deleted in adult cancers and shown to induce leukaemogenesis, however in paediatric AML we found the region to be transcriptionally repressed. In combination, our data highlights the utility of interrogating DNA methylation and microRNA in combination with underlying genetic status to provide novel insights into AML biology.

Validation of DNA methylation biomarkers for diagnosis of acute lymphoblastic leukemia.

BACKGROUND: DNA methylation biomarkers capable of diagnosis and subtyping have been found for many cancers. Fifteen such markers have previously been identified for pediatric acute lymphoblastic leukemia (ALL). Validation of these markers is necessary to assess their clinical utility for molecular diagnostics. Substantial efficiencies could be achieved with these DNA methylation markers for disease tracking with potential to replace patient-specific genetic testing. METHODS: We evaluated DNA methylation of promoter regions of TLX3 (T-cell leukemia homeobox) and FOXE3 (forkhead box E3) in bone marrow biopsies from 197 patients classified as leukemic (n = 95) or clear of the disease (n = 102) by MALDI-TOF. Using a single nucleotide extension assay (methylSABER), we tested 10 bone marrow biopsies collected throughout the course of patient chemotherapy. Using reference materials, diagnostic thresholds and limits of detection were characterized for both methods. RESULTS: Reliable detection of DNA methylation of TLX3 and FOXE3 segregated ALL from those clear of disease with minimal false-negative and false-positive results. The limit of detection with MALDI-TOF was 1000-5000 copies of methylated allele. For methylSABER, the limit of detection was 10 copies of methylated TLX3, which enabled monitoring of minimal residual disease in ALL patients. CONCLUSIONS: Mass spectrometry procedures can be used to regionally multiplex and detect rare DNA methylation events, establish DNA methylation loci as clinically applicable biomarkers for disease diagnosis, and track pediatric ALL.

Exploring the utility of human DNA methylation arrays for profiling mouse genomic DNA.

Illumina Infinium Human Methylation (HM) BeadChips are widely used for measuring genome-scale DNA methylation, particularly in relation to epigenome-wide association studies (EWAS) studies. The methylation profile of human samples can be assessed accurately and reproducibly using the HM27 BeadChip (27,578 CpG sites) or its successor, the HM450 BeadChip (482,421 CpG sites). To date no mouse equivalent has been developed, greatly hindering the application of this methodology to the wide range of valuable murine models of disease and development currently in existence. We found 1308 and 13,715 probes from HM27 and HM450 BeadChip respectively, uniquely matched the bisulfite converted reference mouse genome (mm9). We demonstrate reproducible measurements of DNA methylation at these probes in a range of mouse tissue samples and in a murine cell line model of acute myeloid leukaemia. In the absence of a mouse counterpart, the Infinium Human Methylation BeadChip arrays have utility for methylation profiling in non-human species.

The use of DNA from archival dried blood spots with the Infinium HumanMethylation450 array.

BACKGROUND: Dried blood (Guthrie card) spots provide an efficient way to collect and store blood specimens. DNA from this source has been utilised for a number of molecular analyses including genome-wide association studies, but only few studies have tested the feasibility of using it for epigenetic applications, particularly at a genome-wide level. RESULTS: In this study, we demonstrate the successful use of DNA isolated from archived dried blood spots for the Infinium HumanMethylation450 Beadchip, along with DNA from matched frozen buffy coats. We obtained high quality and reproducible genome-wide DNA methylation profiles using both sample types. We also report high correlations (r > 0.9907) between DNA obtained from matched dried blood spots and frozen buffy coats, sufficient to distinguish between unrelated individuals. CONCLUSIONS: We, thus, demonstrate that DNA from archived dried blood spots is suitable for genome-wide DNA methylation profiling.

FXN methylation predicts expression and clinical outcome in Friedreich ataxia.

OBJECTIVE: Friedreich ataxia (FA) is the most common ataxia and results from an expanded GAA repeat in the first intron of FXN. This leads to epigenetic modifications and reduced frataxin. We investigated the relationships between genetic, epigenetic, and clinical parameters in a large case-control study of FA. METHODS: Clinical data and samples were obtained from individuals with FA during annual visits to our dedicated FA clinic. GAA expansions were evaluated by polymerase chain reaction (PCR) and restriction endonuclease digest. DNA methylation was measured using bisulfite-based EpiTYPER MassARRAY (Sequenom, San Diego, CA). FXN expression was determined using real-time reverse transcriptase PCR. Significant correlations between the different parameters were examined using the nonparametric Spearman rank correlation coefficient, as well as univariate and multivariate regression modeling. RESULTS: Characteristic DNA methylation was identified upstream and downstream of the expansion, and validated in an independent FA cohort. Univariate and multivariate analyses showed significant inverse correlations between upstream methylation and FXN expression, and variation in downstream methylation and age of onset. FXN expression also inversely correlated with the Friedreich Ataxia Rating Scale score, an indicator of disease severity. INTERPRETATION: These novel findings provide compelling evidence for the link between the GAA expansion, the DNA methylation profile, FXN expression, and clinical outcome in FA. Epigenetic profiling of FXN could be used to gain greater insight into disease onset and progression, but also as a biomarker to learn more about specific treatment responses and pharmacological mechanism(s). This work also highlights the potential for developing therapies aimed at increasing frataxin levels to treat this debilitating disease.

UHRF1/UBE2L6/UBR4-mediated ubiquitination regulates EZH2 abundance and thereby melanocytic differentiation phenotypes in melanoma.

Cellular heterogeneity in cancer is linked to disease progression and therapy response, although mechanisms regulating distinct cellular states within tumors are not well understood. We identified melanin pigment content as a major source of cellular heterogeneity in melanoma and compared RNAseq data from high-pigmented (HPCs) and low-pigmented melanoma cells (LPCs), suggesting EZH2 as a master regulator of these states. EZH2 protein was found to be upregulated in LPCs and inversely correlated with melanin deposition in pigmented patient melanomas. Surprisingly, conventional EZH2 methyltransferase inhibitors, GSK126 and EPZ6438, had no effect on LPC survival, clonogenicity and pigmentation, despite fully inhibiting methyltransferase activity. In contrast, EZH2 silencing by siRNA or degradation by DZNep or MS1943 inhibited growth of LPCs and induced HPCs. As the proteasomal inhibitor MG132 induced EZH2 protein in HPCs, we evaluated ubiquitin pathway proteins in HPC vs LPCs. Biochemical assays and animal studies demonstrated that in LPCs, the E2-conjugating enzyme UBE2L6 depletes EZH2 protein in cooperation with UBR4, an E3 ligase, via ubiquitination at EZH2's K381 residue, and is downregulated in LPCs by UHRF1-mediated CpG methylation. Targeting UHRF1/UBE2L6/UBR4-mediated regulation of EZH2 offers potential for modulating the activity of this oncoprotein in contexts in which conventional EZH2 methyltransferase inhibitors are ineffective.

Granulin-epithelin precursor and ATP-dependent binding cassette (ABC)B5 regulate liver cancer cell chemoresistance.

BACKGROUND & AIMS: Chemotherapy is used to treat unresectable liver cancer with marginal efficacy; this might result from hepatic cancer cells with stem cell and chemoresistant features. Gene expression profiling studies have shown that hepatic cancer cells express granulin-epithelin precursor (GEP); we investigated its role in hepatic cancer stem cell functions and chemoresistance. METHODS: The effects of GEP and drug transporter signaling on chemoresistance were investigated in hepatic cancer stem cells. We analyzed the expression patterns of 142 clinical samples from liver tumors, adjacent nontumorous liver tissue, and liver tissue from patients who did not have cancer. RESULTS: GEP regulated the expression of the adenosine triphosphate-dependent binding cassette (ABC)B5 drug transporter in liver cancer cells. Chemoresistant cells that expressed GEP had increased levels of ABCB5; suppression of ABCB5 sensitized the cells to doxorubicin uptake and apoptosis. Most cells that expressed GEP and ABCB5 also expressed the hepatic cancer stem cell markers CD133 and EpCAM; blocking ABCB5 reduced their expression. Expression levels of GEP and ABCB5 were correlated in human liver tumor samples. ABCB5 levels were increased in liver cancer cells compared with nontumor liver tissue from patients with cirrhosis or hepatitis, or normal liver tissue. ABCB5 expression was associated with the recurrence of hepatocellular carcinoma after partial hepatectomy. CONCLUSIONS: Expression of GEP and ABCB5 in liver cancer stem cells is associated with chemoresistance and reduced survival times of patients with hepatocellular carcinoma. Reagents designed to target these proteins might be developed as therapeutics and given in combination with chemotherapy to patients with liver cancer.

Epigenetic silencing of BIM in glucocorticoid poor-responsive pediatric acute lymphoblastic leukemia, and its reversal by histone deacetylase inhibition.

Glucocorticoids play a critical role in the therapy of lymphoid malignancies, including pediatric acute lymphoblastic leukemia (ALL), although the mechanisms underlying cellular resistance remain unclear. We report glucocorticoid resistance attributable to epigenetic silencing of the BIM gene in pediatric ALL biopsies and xenografts established in immune-deficient mice from direct patient explants as well as a therapeutic approach to reverse resistance in vivo. Glucocorticoid resistance in ALL xenografts was consistently associated with failure to up-regulate BIM expression after dexamethasone exposure despite confirmation of a functional glucocorticoid receptor. Although a comprehensive assessment of BIM CpG island methylation revealed no consistent changes, glucocorticoid resistance in xenografts and patient biopsies significantly correlated with decreased histone H3 acetylation. Moreover, the histone deacetylase inhibitor vorinostat relieved BIM repression and exerted synergistic antileukemic efficacy with dexamethasone in vitro and in vivo. These findings provide a novel therapeutic strategy to reverse glucocorticoid resistance and improve outcome for high-risk pediatric ALL.

Gut-derived short-chain fatty acids modulate skin barrier integrity by promoting keratinocyte metabolism and differentiation.

Barrier integrity is central to the maintenance of healthy immunological homeostasis. Impaired skin barrier function is linked with enhanced allergen sensitization and the development of diseases such as atopic dermatitis (AD), which can precede the development of other allergic disorders, for example, food allergies and asthma. Epidemiological evidence indicates that children suffering from allergies have lower levels of dietary fibre-derived short-chain fatty acids (SCFA). Using an experimental model of AD-like skin inflammation, we report that a fermentable fibre-rich diet alleviates systemic allergen sensitization and disease severity. The gut-skin axis underpins this phenomenon through SCFA production, particularly butyrate, which strengthens skin barrier function by altering mitochondrial metabolism of epidermal keratinocytes and the production of key structural components. Our results demonstrate that dietary fibre and SCFA improve epidermal barrier integrity, ultimately limiting early allergen sensitization and disease development.The Graphical Abstract was designed using Servier Medical Art images ( https://smart.servier.com ).